Sasha was about 8 months old when all of sudden she srted holding it at night and then started "asking" to go out. One of the biggest things was using the word "potty" with her every single time she went out and was going... and then asking her when she would wake me up in the morning and again before bed "Sasha do you need to go potty?" Taking her out as soon as I got home helped too... So, it really came down to taking her out regualarly, creating a cue, reinforcing by talking to her when she was doing the right thing and making it fun. Cause going out should not just be about going potty... Making certain she was playing before and after was important too.
Trevor